Many traditional machining processes utilize a “wet machining” process that requires the application of a large quantity of lubricating coolant to an interface between a cutting tool and a workpiece during a machining process. Such machining processes may include milling, drilling, tapping, and finish machining, for example. The lubricating coolant used may be water or oil-based, and such machining processes may require the delivery of several gallons per hour of the lubricating coolant to the cutting edge of the cutting tool to maintain a thermal stability of the machine tooling and the workpiece. The wet machining process may also be used to desirably relocate chips that are removed from the workpiece as a result of the machining process.
However, use of traditional wet machining processes can be problematic due to the additional expense required to maintain a system utilizing such large quantities of lubricating coolant. For instance, it has been estimated that the costs associated with the use of a suitable lubricating coolant in a wet machining process can be as much as 15% or more of the life-cycle operational cost of the machining process. These costs may include the expenses associated with procuring, filtering, or separating the lubricating coolant, as well as expenses related to keeping records and disposing of the lubricating coolant in accordance with any applicable rules or regulations related to the use of such coolants.
Wet machining processes also present additional safety and health concerns for those who operate such systems. Traditional wet machining often results in the formation of a coolant mist that may interact with the remainder of the work shop where the wet machining is being performed. The coolant mist may present health concerns due to its toxicity and the generation of bacteria or fungi associated with the coolant.
One solution to the problems associated with wet machining is the use of minimum quantity lubrication (MQL) machining processes. An MQL machining process is a nearly dry machining process that uses a small quantity of a lubricant, such as vegetable or ester-based oil, mixed with a gas such as air to form an aerosol for lubricating a cutting tool surface during a machining process. MQL machining requires only milliliters of lubricant to be delivered to the cutting edge of the tool per hour as opposed to the gallons of coolant per hour associated with a wet machining process. This significant reduction in the use of lubricant causes an MQL machining process to reduce the exposure of workers to the harmful coolant mists used in wet machining processes, to reduce the amount of materials that must be disposed of following the machining process, and to produce nearly dry and virtually clean metal chips that are much easier to recycle.
Many cutting tools used to carry out an MQL process require internal passages or ducts to supply the air and oil aerosol to the cutting edge of the tool. Such MQL machining processes require that the aerosol flowing through such passages be precisely metered to maintain optimum wetting and lubrication properties, depending on the type of cutting operation. If the aerosol passing through the passages formed in the cutting tool encounters a significant pressure drop or for any other reason is not allowed to flow freely during rotation of the cutting tool the aerosol will reclassify as a larger globule of oil, and the precisely selected lubricity properties of the aerosol will be lost. The resulting loss of lubrication may cause significant damage to the cutting tool, the workpiece, or both.
Additionally, the degree of pressure drop encountered by a lubricating aerosol is often directly affected by the shape and configuration of the fluid conduit through which the lubricating aerosol is caused to flow. Even minor changes in the diameter or curvature of such a fluid conduit can have significant effects on the degree of pressure drop encountered by the lubricating aerosol as it traverses the fluid conduit. Accordingly, it is important that any fluid conduits used to distribute such a lubricating aerosol are precision manufactured to ensure that the lubricating aerosol is delivered to each of the cutting edges of the cutting tool while having a pressure suitable for preventing the separation of the lubricating oil and the air forming the lubricating aerosol.
It would therefore be desirable to create a tool that includes internal fluid conduits that are precision manufactured to militate against causing a pressure drop in a lubricating aerosol traversing the internal fluid conduits during a cutting operation of the tool.